Nutrients

The Problem

  • There are many minerals which, under normal circumstances, are essential to the growth and health of living organisms. However, under certain circumstances, these nutrients accumulate to unnaturally high concentrations, leading to adverse biological and environmental effects.
  • Most nutrient pollution involves a process known as "eutrophication." Nutrients enrich the water and some groups of microscopic algae begin to grow densely, or "bloom." In extreme situations, the algae bloom in quantities far beyond what can be consumed by the animals that graze on them, and as the algae die, they decompose.
  • This decomposition consumes large amounts of oxygen (and releases carbon dioxide) until the water finally becomes totally oxygen-deprived or "anoxic," causing animals in the area to die or flee.
  • The endpoint of such eutrophication is known as a "dead zone."
  • The most extensive dead zone is at the mouth of the Mississippi River, reaching far into the Gulf of Mexico, encompassing as much as 7,000 square miles in area. It is largely the result of continuous over fertilization of the area by river water laden with fertilizers running off the central farmlands of the US.
  • Elsewhere, the New York Bight receives sewage outflow and urban runoff along with the outflow of several river systems. Although the sewage is treated, the process does not fully remove nutrients, so coastal waters are fertilized leading to extreme eutrophication, especially during the calmer periods of summer.

The Causes

  • Nutrient pollution can be caused by such common human activities as growing food, getting rid of bodily wastes, washing clothes and driving cars.
  • Nitrogen and phosphorous are major components of commercial fertilizers used extensively in agriculture, tree culture and lawn care. They can be carried by soil erosion and runoff to rivers, lakes and coastal waters; because these systems are naturally poor in both phosphorous and nitrogen, the nutrients addition can have substantial and immediate effects.
  • Because human excrement is rich in nitrogen and many household cleaning products contain phosphorous, sewage and septic tanks are major sources of nutrient pollution. Similarly, farm and aquaculture animals produce significant amount of nitrogen-rich wastes.
  • The combustion of fossil fuels releases nitrogen-rich compounds into the air, and these rain on and dissolve into lake, estuary and coastal waters downwind. Automobiles and coal-burning power plants are serious contributors to eutrophication, sometimes accounting for as much as ;50 percent or 40 percent of the nitrogen in a body of water or coastal ocean area.

The Context

  • Nutrient pollution in coastal marine environments is a direct result of three phenomena: human population increase; increased chemical-based farming and intensive animal husbandry; and the expanding use of fossil fuels. These all occur globally but, in particular locales, take on more or less importance relative to each other, so solutions may vary.

The Solutions

  • Reducing the waste of water in irrigation and water supply systems would help maintain higher flow rates in rivers and thus reduce nutrient pollution.
  • Improved sewage treatment can substantially reduce nutrient input. Many nations may have no sewage treatment at all, or only primary treatment, which removes only bulky materials and some suspended particles. Other countries, such as the US. have more expensive secondary treatment, which means that less nutrient-rich organic material is discharged into the water. However, only tertiary treatment, which is rare and even snore expensive, will fully remove dissolved nutrients from Water discharge.
  • Alternatives to large sewage plants including biological toilets, which break human excrement into a form that can be used as fertilizer; and constructed wetlands, which can filter sewage water from a small community or complex so that the water which flows out of the wetland is clean.
  • Nutrient pollution from agriculture can be reduced significantly by alternative agriculture practices such as the use of organic fertilizer and reductions in overall fertilizer use; planting tree buffers around streams and ponds, and building wetlands; and underground composting and re-use (as fertilizer) of animal wastes.
  • Nitrogen pollution can be reduced by using less fossil fuel and by cleaner burning of those fuels. Reductions can be accomplished by manufacturing cars with better gas mileage; by designing and using more efficient motors and heating systems; by designing and using low energy appliances and lights; by improving the filtering and scrubbing of emissions from power plants; and simply by using less fuel and electricity.